Question

which C-C bond length is minimum in the following compounds?
a.C6H6
b.C2H6
c.C2H4
d.C2H2​

Answer 1

Answer:

(d) Acetylene

Explanation:

We know, that there are only sigma bonds in ethane (C₂H₆), one sigma and one PI bond in ethene (C₂H₄), and one sigma and two PI bonds in acetylene (C₂H₂). Benzene (C₆H₆) is an aromatic compound, and due to resonance, there is partial double bonds everywhere.

Now, hybridization of carbons of alkane is sp³, that of alkene is sp², and that of alkyne is sp. Thus, in sp, there's an increased s-character, that reduces the bond length.

Further, bond length is indirectly proportional to bond strength. We know, that the bond strength of an alkyne > alkene > benzene > alkane (because of course, triple bond is the strongest). So, the order of bond length will be the reverse, i.e.,

Alkane (b) > Benzene (a) > Alkene (c) > Alkyne (d).

So, alkyne (here, option d, acetylene) is having the minimum bond length.

Hope this helps. Thanks!